The present invention relates to suspension systems for road vehicles, for example for air suspension systems adapted for heavy vehicles such as trucks and buses. Moreover, the invention also relates to methods of providing suspension for such road vehicles.
Contemporary road vehicles are provided with suspension systems functionally included between wheels and chassis thereof. These suspension systems are operable to accommodate and dampen vertical movement of the wheels when such vehicles are in motion, such movement arising in response to, for example, uneven road surfaces. Thus, the suspension systems are adapted to reduce a magnitude of mechanical shocks being transmitted via the suspension systems to the chassis. Moreover, such suspension systems are necessary to enhance comfort of persons travelling in the vehicles, and also to reduce damage to objects, for example goods, being transported in the vehicles. Furthermore, accommodation and dampening of vertical motion is especially important in commercial road vehicles, for example in trucks operable to transport relative large quantities of fragile goods. Commercial road vehicles are often heavy, for example weighing several tonnes, and are capable of transporting goods of comparable weight. Moreover, such weights require suspensions systems of considerable strength to provide efficient shock absorbing functionality, such strength requirements conventionally requiring the suspension systems to add to vehicle height and compromising designs of such vehicles.
In order to be more effective, suspension systems need to be operable to provide for degrees of freedom of motion in certain direction and yet be stiff in other directions of motion, for example to prevent associated road vehicles having a tendency to roll which can be potentially dangerous, especially when the road vehicles are required to bear their loads at relatively elevated height. It is a considerable technical challenge to provide enhanced suspension systems in road vehicles in which severe height and compactness constraints are imposed of designers of such road vehicles.
In a published U.S. Pat. No. 6,209,895, there is described an axle suspension system for a wheeled road vehicle. The suspension system includes at each side of the vehicle a trailing arm beam pivotally connected at a proximate end thereof via a resilient pivotal bushing to a hanger of a chassis of the vehicle. An air spring is mounted substantially at a distal end of the trailing arm beam between the trailing arm beam and the vehicle chassis. A transversely extending vehicle axle is mounted substantially to the distal ends of the trailing arm beams via “U”-shaped bolts and a bushing held by nuts in a conventional manner. A shock absorber is mounted between the vehicle chassis and the trailing arm beam.
The suspension system also includes connections between the vehicle axle and the trailing arm beams to reduce stress concentrations spatially where the trailing arm beams are connected to the vehicle axle. Such stresses are reduced by employing a special form of axle cradle which extends laterally beyond sides of each trailing arm beam. To further dissipate stresses, sponsons are attached to each trailing arm beam on opposite sides thereof to provide additional support to the axle cradle and thereby dissipate the stresses being transmitted in operation from the axle cradle over a greater expanse of the trailing arm beams.
In a published European patent no. EP 0 940 321, there is described a suspension system for a heavy duty vehicle. The system comprises suspension units, wherein each suspension unit includes a spring and a telescopic damper fitted between a chassis of the vehicle and a beam axle thereof. Ends of the beam axle are braced on the chassis by trailing arms which are linked to the chassis via mounting blocks. The suspension system further comprises a transverse stabilizer connected at a first end thereof to a bottom end of a suspension bracket, and at a second end thereof to the beam axle. The stabilizer is implemented in a manner akin to a contemporary Panhard rod for resisting a lateral rolling motion of the vehicle.
Convention suspension systems, for example the systems described in the aforesaid U.S. Pat. No. 6,209,895 and also the European patent no. EP 0 940 321, suffer certain drawbacks which the present invention seeks to address. For example, the conventional systems are often insufficiently compact which compromises vehicle design, for example regarding beneficial location of wheel axles so as to better dynamically bear loads of associated vehicles. Moreover, the systems do not include their air springs located in most favourable positions. Furthermore, the conventional systems do not provide desirably resilient roll characteristics which are important to optimize to prevent vehicles swaying can result in vehicles swaying when corning which can potentially affect vehicle dynamic handling characteristics.
Thus, contemporary suspension systems are constrained in how their various suspension elements can be spatially disposed and mounted and in what combination they can be configured. Such constraints can potentially provide in operation non-optimal suspension characteristics.
It is desirable to provide an improved suspension system which is operable to address aforementioned limitations encountered with contemporary suspension systems, for example to enable suspension components to be included in such a manner so as to provide for more flexible design and a decrease in height build up of a vehicle.
According to a first aspect of the present invention, there is provided a suspension system operable to provide a suspension between wheels and a frame of a vehicle, said system comprising one or more arm beams, each arm beam being substantially pivotally mounted to the frame at its proximate end and coupled substantially at its distal end to a guiding assembly operable to enable the arm beam to pivot in substantially a vertical direction and to be substantially restrained in lateral directions substantially perpendicular to said vertical direction, wherein each arm beam further includes:
(a) a spring and damper assembly near or at its distal end for providing a dampened resilient mount for said suspension;
(b) a wheel axle beam coupled to the said one or more arm beams so that in operation a load borne by the wheels of the vehicle is transmitted directly substantially in-line with a central axis of said spring and damper assembly; and
(c) a stabilizing arrangement coupled between the arm beam and the frame, the stabilizing arrangement being operable to at least partially resist a lateral rolling motion of said vehicle by way of torsional compliance exhibited by the stabilizing arrangement, said suspension system being configured so that said stabilizing arrangement is included between the proximate end of the one or more arm beams and their damper and spring assemblies for rendering the suspension system more compact.
The present invention is of advantage in that capable of providing a more compact and improved suspension system for vehicles.
Optionally, in the suspension system, the stabilizing arrangement includes a stabilizing member mounted in respect of said wheel axle beam via a plurality of bushing components, said plurality of bushing components enabling at least limited rotation of said stabilizing member relative to said wheel axle beam, said stabilizing member being provided with substantially mutually parallel orthogonal end portions adapted to be anchored in respect of said frame via pivotally-mounted linking members, said orthogonal end portions being deployed in operation substantially parallel to said one or more arm beams.
Optionally, in the suspension system, the spring and damper assembly includes at least one of: an air spring, a feather spring, a coil spring.
Optionally, in the suspension system, the guiding assembly comprises pivotally mounted first and second interfacing members substantially pivotally coupled via a pivoting region to said distal end of each arm beam.
Optionally, in the suspension system, the first interfacing member is coupled between the distal end of its associated arm beam and a first pivot, and the second interfacing member is coupled between said first pivot and a second pivot said second pivot being mounted in respect of said frame.
Optionally, in the suspension system, the one or more beam arms are implemented in operation as trailing beam arms.
Optionally, the suspension system is adapted for a front wheel set of the vehicle.
Optionally, alternatively, the suspension system is adapted for a rear wheel set of said vehicle.
According to a second aspect of the invention, there is provided a vehicle comprising a suspension system; the suspension system is implemented according to the first aspect of the invention.
It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention as defined by the accompanying claim set.